larrytoelle
Full Time Senior Member
Posts: 3735
Loc: Fort Jones, California .....
Reg: 01-20-03
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 01-27-04 03:02 PM - Post#35058
Howdy,
As I suspected, on the initial setup flights, the mainshaft was damaged. Oddly, nothing else seems broken or even seriously nicked or dinged. The one crash wasn't that serious, but it did permanently upset blade tracking.
Upon inspection, it was obvious that the head was not spinning on center or trued to the mainshaft. If it were a steel mainshaft, I would have immediately thought that it was bent. But it's a CF shaft, so it was a bit of a mystery.
SHAFT REMOVAL
Removal is relatively simple. Remove the main blades. Disconnect the two ball links connecting the swash to the servos. Remove the steel pin that retains the rotor head and slip the head and swash plate from top of the shaft.
Normally, you should be able remove the shaft and main gear through the bottom of the bird, but in this case the damage was to the top of the shaft and it was necessary to remove the steel pin securing the main gear and remove the shaft from the top.
In this case, the CF shaft had split near the top. I would guess the split is the result of a twist to the shaft when the main blades struck. The steel pin that secures the head would have twisted in the mainshaft and fractured the CF lengthwise ... the weakest link in CF.
A repair to the shaft may be possible with CA glue, but I've opted to order another shaft. Also, AV8ER indicated that he'd received a steel shaft replacement, which in my opinion, would be a better main shaft for this bird.
ORDERING
A "GOOGLE" search for "smartech aerohawk parts" yield only two sources ... http://www.raidentech.com/raidentech168/smhesppa.html and http://www.hobbytron.net/helicopters.html?gtse=goog>kw=smartech+aerohawk+parts.
Raidentech's prices were significantly less than Hobbytron ... so Raidentech got the order.
On Raidentech's site, there are two items referred to as a main axes ... mainshaft part #19244 and #19245. There is a small picture of #19245 which appears to be a steel shaft with a c-clip ... which I'm guessing ... will obviate the need for the shaft collar mod. The c-clip appears to fix the problem with the rubber tube that holds the mainshaft in place ... we'll see. I ordered both parts so we can find out what the differences are.
HUMMINGBIRD v. AEROHAWK
Comparing the mainshaft from the Aerohawk to the Hummingbird, it's immediately obvious that these two parts are not interchangeable. Although both are 3mm shafts, the Hummingbird shaft is perhaps 30mm longer. Also, the Aerohawk shaft has flat spots (forgot what this is called) to retain the maingear and rotor head. A round shaft will not fit the head, but perhaps will fit the maingear.
I groused through my junk pile to locate a 3mm shaft to fabricate one, but couldn't find 3mm stock rod. It wouldn't take that much to make your own ... but at less than $3 ... it's not that expensive to order one either.
While I had the swash plate off, I had a chance to compare it to the Hummer swash. They're similar, but the Aerohawk's pin that slides in the anti-rotation bracket would be too short to fit the Hummer ... but it appears that Hummer Swash would fit the Aerohawk. The Hummer's swash plate's finish is noticeably better ... it appears to have been machined with more care. The bearing quality is really the only consideration here, and I have no idea which would be better.
Also, I noticed that the Aerohawk's ball ends were less than smooth ... and do bind. Before reassembling, I'll smooth the round ball ends with rubbing compound and ensure that the balls and links work freely. Any binding in this mechanism, will make controls erratic and expend additional battery to overcome the binding.
While the main gear was off, I noticed that brass from the pinion gear was finding its way to the main gear. I've adjusted the gear mesh, so I'm reasonably sure that there's not a problem with mesh. I'm guessing that the general finish of the teeth on either or both pinion and main are wearing the other. Perhaps in time, the two components will better mate with each other, but for now, they're not happy with each other.
I'll let you know when the new parts arrive and how things work out.
LT
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